For processing chunky products to be filled, such as structurally viscous fluids or beverages containing small pieces, fibers, pulps, fruit cells, particles or the like, in the beverage and food industry, in particular in processing in filling, fruit juice preparation, dairy or brewery process plants, for the calculated design of process plant equipment, such as heat exchangers, fillers, valves, and piping systems, the determination of the viscosity of the fluid or beverage to be processed, also under the influence of temperature, is extremely important, for example also to be able to assess forms of flow and residence times, and as a basis for numerical simulations and technical calculations, or as a basis for the designing of the process plant. Usually, rheometers are employed to determine the viscosity of such fluids or beverages critical with respect to the determination of their absolute viscosity, where the determination of viscosity depending on the shearing rate is reliant on a defined gap in the measuring system. These are, for example, plate/plate or cylinder/bowl systems by Searl or Couette. In these measuring systems, excessively large pieces, fibers, etc. can lead to blocking or shearing of pieces, resulting in wrong/invalid measured values. Moreover, the possibly too liquid medium in the fluids or beverages often lead to invalid measured values, in particular at higher shearing rate ranges, for example by increasing turbulences in the measuring gap, by burbling or flow fronts with eddies or inhomogeneities in the product which impede the formation of a laminar flow required for measuring. With greater shearing rates, gap emptying can also occur, in particular in case of rather long gap distances that become necessary in case of rather large particles. At lower shearing rate ranges, however, wall slip effects can occur in gap regions, leading to wrong wall shearing speeds in particular in case of rather large shearing gaps and media with yield points. Thus, incorrect torques are formed in the rheometer. These lead to invalid measured values.
Tube rheometers with a straight meter tube, a helical meter tube or an upright U-type meter tube and a pump, as well as flow control means are furthermore discussed in EP 0 458 391 A, DE 10 2005 024 575 B4, U.S. Pat. No. 5,315,863 A, DE 4111295 C2, for example for applications in ground-boring technology.